1. Field of the Invention
The present invention relates to an optical waveguide for a touch panel, and a touch panel employing the optical waveguide.
2. Description of the Related Art
Touch panels are input devices for operating an apparatus by directly touching a display screen of a liquid crystal display device or the like by a finger, a special stylus or the like, and include a display which displays operation items, and detection means which detects the position (coordinates) of a portion of the display screen of the display touched by the finger or the like. Information of the touch position detected by the detection means is sent in the form of a signal to the apparatus, which in turn performs an operation specified by the touch position. Examples of the apparatus employing such a touch panel include ATMs in banking facilities, ticket venders in stations and portable game machines.
A detection device employing an optical waveguide is proposed as the detection means for detecting the finger touch position on the touch panel (see, for example, US2004/0201579A1). As shown in a plan view of FIG. 6, the optical waveguide is disposed around a periphery of a display screen of a rectangular display 31, and includes an L-shaped optical waveguide B1 including a multiplicity of light emitting cores which emit light beams W parallel to the display screen of the display 31, and two linear optical waveguides B2, B3 including a multiplicity of light receiving cores which respectively receive the light beams W emitted from linear portions of the L-shaped optical waveguide B1. Thus, these three optical waveguides B1, B2, B3 cause the light beams W to travel in a lattice form on the display screen of the display 31 (the light beams W are illustrated in a simplified manner in FIG. 6) When a portion of the display screen of the display 31 is touched by the finger in this state, the finger blocks some of the light beams W. Therefore, the position of the portion touched by the finger is detected by detecting a light blocked portion by the two linear optical waveguides B2, B3.
In the case of the touch panel of US2004/0201579A1, however, unless the two linear optical waveguides B2, B3 which receive the light beams W are accurately positioned with respect to the L-shaped optical waveguide B1 which emits the light beams W, the optical waveguides B2, B3 cannot receive the light beams W, failing to function as the detection means. In addition, end faces of the respective cores serving as light output/input surfaces each have a very small size, so that the accurate positioning requires tremendous effort and time.